In recent years, the following materials have been used as the material of a base body for a cutting tool: a sintered alloy such as a cemented carbide alloy or cermet, a high-hardness sintered compact such as diamond or cubic boron nitride (cBN), and ceramics such as alumina or silicon nitride. A cutting tool with a coating layer on the surface of this base body is used. In the manufacturing of this cutting tool, a technique is used by which the coating layer is formed to improve wear resistance, slidability, and fracture resistance.
A physical vapor deposition such as an ion plating or a sputtering is used as an example of a method of forming the coating layer. A study on a coating layer made of nitride having Ti or Al as a main constituent is actively being conducted, and continuous improvement thereon is being made. In addition to a coating material, various innovations are applied to a cutting tool so as to cope with a change in cutting conditions such as an increase in cutting speed or the diversification of a workpiece.
For example, in a cutting tool disclosed in PTL 1 and PTL 2, the surface of a base body is coated with a film made of TiAIN or the like using the ion plating, and a coating film for a cutting edge of the cutting tool has a ratio of Ti greater than that of a flat portion of the cutting tool by increasing the absolute value of a negative bias applied during a film deposition in a later phase of the film deposition after an initial phase thereof.